摘要
我们基于分子动力学(Molecular Dynamics),建立了石墨烯纳米压痕实验的数值模型,以模拟压痕实验过程,得到典型实验过程的力-位移曲线,并进而讨论压头下压速度,压头半径以及边界条件等因素对实验结果的影响.论文测得石墨烯弹性模量为1TPa,强度为240GPa.加载过程中,压头加载到临界压入深度hc时,石墨烯试件在压头处撕裂破坏.给定最大压入深度,对石墨烯进行加载—卸载—再加载试验,发现当最大压入深度hmax小于hc时,石墨烯发生的是完全弹性变形;当最大压入深度hmax大于hc时,卸载和再加载过程中石墨烯能基本恢复原貌,但仍有少数C—C键较长而无法恢复,成为石墨烯再加载时的破坏起点,石墨烯的破坏力和位移都显著下降.另外,还发现大于0.05nm/ps的压头速度和压头半径对石墨烯临界压入深度和破坏力都有显著影响.
Molecular dynamics simulation of nanoindentation experiment on single layer graphene sheets is carried out. A typical force-displacement curve is obtained and the effects of various factors including indenter radius, velocities as well as boundary conditions on the simulation results are discussed. The Young＇s modulus and the strength of the graphene are measured as 1 terepascals and 240 gigapascals, respectively. Observation of the deformation process shows that the graphene rips from the central point at a critical indentation depth he. It is found from the loading-unloading-reloading processes of different maximum indentation depth hmax that the graphene undergoes entire elastic deformation if hmax is less than he. However, when hmax is larger than he, fracture appears in the graphene from the irregular hexagon formed by lengthened C--C bonds upon loading. When unloaded and reloaded the graphene can largely reinstate though with a few bonds of carbon atoms being much longer than their original lengths Easier ripping of the graphene may initiate from these bonds, which in turn, results in significant decrease of strength and deformation of the graphene. Additionally, a loading speed of higher than 0.05 nm/ps and the radius of the indenter have remarkable effects on the critical indentation depth and force. These results are significant for the application of nanoindentation in characterizing the mechanical properties of graphene accurately.
出处
《中国科学：物理学、力学、天文学》
CSCD
北大核心
2010年第3期353-360,共8页
Scientia Sinica Physica,Mechanica & Astronomica
基金
上海市科学技术委员会基础研究重点项目资助(批准号:09JC1414400)
